Speaker: Prof. Eung Jin Chun (KIAS)
Talk title: Spontaneous Leptogenesis in Type I Seesaw
Time: 2025/12/08 (Mon.) 12:30
Place: NCTS Physics 4F Lecture Hall, Cosmology Hall, NTU

Abstract: 
Type-I seesaw models with a spontaneously broken B−L symmetry provide a natural framework for spontaneous leptogenesis driven by a Majoron. The kinetic background of the Majoron acts as the CP-violating source, generating lepton asymmetry both in the decay of right-handed neutrinos and during equilibration through inverse-decay processes. We formulate the Boltzmann equations incorporating both effects consistently to enable a quantitative analysis. The resulting asymmetry either tracks its equilibrium value when the neutrino Yukawa coupling is sufficiently large to keep B−L violation in equilibrium. Otherwise, an interesting interplay emerges between decay and inverse-decay dynamics, depending on the Yukawa coupling strength and the initial abundance of right-handed neutrinos.